NH4B11O16(OH)2: a new ammonium borate with wavy-shaped polycyclic 2∞[B11O16(OH)2] layers

Abstract

The ammonium borate NH₄B₁₁O₁₆(OH)₂ has been successfully synthesized by a mild hydrothermal method. Its structure features a new fundamental building block (FBB) [B₁₁O₁₈(OH)₂], which is composed of a [B₅O₁₀] double-ring and two [B₃O₅(OH)] single-rings via sharing corner oxygen atoms. The FBB further condenses into 2D wavy-shaped polycyclic layers ²_∞[B₁₁O₁₆(OH)₂] and forms the final framework through hydrogen bonding. Specifically, the effect of the hydroxyl to boron ratio (N_OH/N_B) on the FBB assembly has been investigated in the ammonium borate system. In addition, the optical and thermal properties of this compound have been studied experimentally. First-principles calculations have also been carried out in order to understand the electronic structure.